The function of the α1B-adrenergic receptor phosphorylation sites previously detected by mass spectrometry was evaluated by employing mutants, substituting them with non-phosphorylatable amino acids. ...Substitution of the intracellular loop 3 (IL3) sites did not alter baseline or stimulated receptor phosphorylation, whereas substitution of phosphorylation sites in the carboxyl terminus (Ctail) or both domains (IL3/Ctail) markedly decreased receptor phosphorylation. Cells expressing the IL3 or Ctail receptor mutants exhibited a noradrenaline-induced calcium-maximal response similar to those expressing the wild-type receptor, and a shift to the left in the concentration–response curve to noradrenaline was also noticed. Cells expressing the IL3/Ctail mutant exhibited higher apparent potency and increased maximal response to noradrenaline than those expressing the wild-type receptor. Phorbol ester-induced desensitization of the calcium response to noradrenaline was reduced in cells expressing the IL3 mutant and abolished in cells in which the Ctail or the IL3/Ctail were modified. In contrast, desensitization in response to preincubation with noradrenaline was unaffected in cells expressing the distinct receptor mutants. Noradrenaline-induced ERK phosphorylation was surprisingly increased in cells expressing IL3-modified receptors but not in those expressing receptors with the Ctail or IL3/Ctail substitutions. Our data indicate that phosphorylation sites in the IL3 and Ctail domains mediate and regulate α1B-adrenergic receptor function. Phorbol ester-induced desensitization seems to be closely associated with receptor phosphorylation, whereas noradrenaline-induced desensitization likely involves other elements.
The potential application of the primary amine/nitrile pair as a liquid organic hydrogen carrier (LOHC) has been evaluated. Ruthenium complexes of formula (p‐cym)Ru(NHC)Cl2 (NHC=N‐heterocyclic ...carbene) catalyze the acceptorless dehydrogenation of primary amines to nitriles with the formation of molecular hydrogen. Notably, the reaction proceeds without any external additive, under air, and under mild reaction conditions. The catalytic properties of a ruthenium complex supported on the surface of graphene have been explored for reutilization purposes. The ruthenium‐supported catalyst is active for at least 10 runs without any apparent loss of activity. The results obtained in terms of catalytic activity, stability, and recyclability are encouraging for the potential application of the amine/nitrile pair as a LOHC. The main challenge in the dehydrogenation of benzylamines is the selectivity control, such as avoiding the formation of imine byproducts due to transamination reactions. Herein, selectivity has been achieved by using long‐chain primary amines such as dodecylamine. Mechanistic studies have been performed to rationalize the key factors involved in the activity and selectivity of the catalysts in the dehydrogenation of amines. The experimental results suggest that the catalyst resting state contains a coordinated amine.
A system of support: The potential application of the primary amine/nitrile pair as a liquid organic hydrogen carrier (LOHC) has been evaluated. Molecular ruthenium complexes, (p‐cym)Ru(NHC)Cl2 (NHC=N‐heterocyclic carbene; see scheme), are active in the dehydrogenation of primary amines to nitriles with the simultaneous formation of two moles of molecular hydrogen. The reaction proceeds without any external additive under mild conditions.
Curcumin and its analogs, chalcones, and C5-monocarbonyl are molecules of great therapeutic potential, but their poor stability and hydrophobicity have hampered their extensive use in clinical ...trials. Therefore, significant efforts have been made in materials science to improve their physicochemical properties. In this study, we propose dendronization as a synthetic strategy to strengthen some physicochemical properties such as solubility and stability of curcumin and analogs, taking advantage of the click chemistry (CuAAC) to attach second-generation polyester dendrons to the unsaturated cores. The dendronization, with the subsequent formation of aromatic triazole groups as linkers, not only modified the solubility and stability of the molecular systems but also favored the diketo tautomeric form of curcumin, as demonstrated spectroscopically. This result is significant since the diketo tautomer, which preserves the antioxidant properties of curcumin, is the most biologically active form. The hydrophobic/hydrophilic balance, achieved after dendronization, allowed the solubilization of the chromophoric molecules in buffered solutions at relevant pH values (7.4 and 6.4). Furthermore, the stability of all molecules was also upgraded since UV-vis absorption spectra did not exhibit modified profiles after 7 days at physiologic pH. From photochemical stability experiments irradiating at 415 nm, the dendritic derivatives containing triazole linkers were more susceptible to being degraded. All derivatives exhibited emission properties according to the length of each conjugate fragment. Fluorescence experiments evidenced the role of dendrons in preventing emission quenching by aggregation and exhibited differentiated emission behavior depending on the linker type (triazole or ester) between the chromophoric core and the polyester dendrons.
A copper complex bearing an N‐heterocyclic carbene ligand with a pyrene “tail” attached to the backbone has been prepared and supported on reduced graphene oxide (rGO). The free and supported copper ...materials have been employed as homogeneous and heterogeneous catalysts in the functionalization of hydrocarbons such as n‐hexane, cyclohexane, and benzene through incorporation of the CHCO2Et unit from ethyl diazoacetate. The graphene‐anchored complex displays higher reaction rates and induces higher yields than its soluble counterpart, features that can be rationalized in terms of a decrease in electron density at the metal center due to a remote net electronic flux from the supported copper complex to the graphene surface.
Electron density shifted to remote graphene: Anchoring an NHC‐CuI complex onto graphene through a pyrene antenna (see graphic) enhances the catalytic properties of the copper center toward hydrocarbon functionalization by carbene transfer from ethyl diazoacetate.
The compound Ru(p‐cym)(Cl)2(NHC) is an effective catalyst for the room‐temperature coupling of silanes and alcohols with the concomitant formation of molecular hydrogen. High catalyst activity is ...observed for a variety of substrates affording quantitative yields in minutes at room temperature and with a catalyst loading as low as 0.1 mol %. The coupling reaction is thermodynamically and, in the presence of a Ru complex, kinetically favourable and allows rapid molecular hydrogen generation on‐demand at room temperature, under air, and without any additive. The pair silane/alcohol is a potential liquid organic hydrogen carrier (LOHC) for energy storage over long periods in a safe and secure way. Silanes and alcohols are non‐toxic compounds and do not require special handling precautions such as high pressure or an inert atmosphere. These properties enhance the practical applications of the pair silane/alcohol as a good LOHC in the automotive industry. The variety and availability of silanes and alcohols permits a pair combination that fulfils the requirements for developing an efficient LOHC.
On demand! An effective supported ruthenium catalyst on the surface of rGO controls the hydrogen production from hydrosilanes. The hydrogen storage properties show the potential application of the silane/alcohol pair as an efficient liquid organic hydrogen carrier.
Recently, a large number of studies at the experimental level in electrochemical systems for energy storage devices have been performed. However, theoretical approaches are highly desirable to ...understand the physicochemical properties giving rise to energy storage phenomena. This work was intended to provide insights into the insilico design of novel nanocomposite materials formed by the Keggin polyoxometalate SiW12 anchored to an organic functional group φ−X (where φ corresponds to the phenyl group and X=−NH2,−OH,−COH and −COOH) linked to a carbon nanotube. In these systems, the Density of States around the Fermi level is enhanced, giving the composite material the capacity of facile electron transport that may be determinant at the charge/discharge cycling performed in energy storage devices. Charge transfer at the composite materials under study is greatest for the φ−COOH functional group, yielding an enhanced attraction similar to a covalent-type bonding with the SiW12 cluster. The rest of the functional groups induce weak interactions, mediated by van der Waals attractions. Our proposed methodology may represent a tool to develop novel electrode materials based on the composite, that may improve the performance on energy storage devices, such as supercapacitors or Li-ion batteries.
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This article attempts to provide a plausible explanation of a series of expressions used by Pliny the Elder to designate a significant number of communities in Hispania: oppida Latio antiquitus ...donata, oppida Latinorum ueterum, oppidani Latii ueteris, oppida Latii antiqui and oppida ueteris Latii (Plin. HN 3.7, 3.18, 3.24, 3.25, 4.117). These phrases, commonly explained from a chronological or typological viewpoint, encompass fifty Augustan ciuitates, the most important feature of which was the enjoyment of Latin rights before the sources used by Pliny were written under the Early Principate. To address this issue, the meaning and the use of the term oppidum are first examined. In a second stage, the origin and the sense of the adjectives uetus and antiquum, as well as the adverb antiquitus, are analysed. The results suggest that oppida ueteris Latii and its variants may express, in a simple and comprehensible way, the administrative changes that a group of Republican Latin colonies in Hispania underwent through their transformation into municipia Latina during the reign of Augustus.
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